Added #each_url, #each_link, #each_redirect and #each_meta_redirect to Page.
Added #each_url, #each_link, #each_redirect and #each_meta_redirect to Page.

* Included Enumerable into Page, and aliased each to each_url.
* Using the enumerable methods should increase performance,
  by reducing GC load.

postmodern/spidr,laplaceliu/spidr,buren/spidr